CHAPTER 18 - Book Review Questions

Question 1

The following statements concern the neural crest
cells:

(a) They are formed from the medial margin of the
neural plate.
(b) They give rise to the posterior root ganglia.
(c) They do not form the neurons of the autonomic
ganglia.
(d) The Schwann cells of peripheral nerves are not
formed from neural crest cells.
(e) They form the cells of the suprarenal cortex.

Answer 1

B is correct.

• The neural crest cells give rise to the posterior root ganglia (see Fig. 1-18). A. The neural
  crest cells are formed from the lateral margin of the neural plate (see Fig. 1-18). C. The neural crest cells form the neurons of the autonomic ganglia (see Fig.1-18). D. The Schwann cells of peripheral nerves are formed from neural crest cells (see Fig. 1-18). E. The neural crest cells form the cells of the suprarenal medulla (see Fig. 1-18).

Question 2

The following statements concern the developing spinal cord:

(a) The alar plates form the neurons in the anterior
gray columns.
(b) The nerve cells of the sympathetic outflow are
not formed from the basal plates.
(c) In the adult, the lower end of the spinal cord lies
at the level of the lower border of the first lumbar
vertebra.
(d) At birth, the lower end of the spinal cord Iies at
the level of the third sacral vertebra.
(e) The meninges surrounding the spinal cord are
developed from the endoderm.

Answer 2

C is correct.

• In the adult, the lower end of the spinal cord lies at the level of the lower border of the first lumbar vertebra. A. The alar plates form the neurons in the posterior gray columns. B. The nerve cells of the sympathetic outflow are formed from the basal plates. D. At birth, the lower end of the spinal cord lies at the level of the third lumbar vertebra. E. The meninges of the spinal cord are developed from the mesenchyme that surrounds the neural tube.

Question 3

The following statements concern the development
of the brainstem:

(a) The cerebellum is formed from the dorsal part
of the alar plates of the metencephalon.
(b) The neurons of the deep cerebellar nuclei are derived from the matrix cells lining the cavity
of the midbrain vesicle.
(c) The neuroblasts in the dorsal plates will form the
nuclei of the trochlear and oculomotor nerves.
(d) The neuroblasts of the superior and inferior colliculi are also formed from the neurocytes in
the basal plates.
(e) The pons arises from the alar part of the metecephalon with cellular contributions from the alar part of the myelencephalon.

Answer 3

A is correct.

• The cerebellum is formed from the dorsal part of the alar plates of the metencephalon (see Fig. 18-6). B. The neurons of the deep cerebellar nuclei are derived from the matrix cells lining the cavity of the hindbrain vesicle. C. The neuroblasts in the basal plates will form the nuclei of the trochIear and oculomotor nerves. D. The neuroblasts of the superior and inferior colliculi are formed from the neurocytes in the alar plates (see Fig. 18-8). E. The pons arises from the anterior part of the metencephalon, with cellular contributions from the alar part of the myelencephalon.

Question 4

The following statements concern the fate of the forebrain vesicle:

(a) The optic vesicle grows out of the midbrain
vesicle.
(b) The thalamus is formed from the alar plates in
the medial walls of the diencephalon.
(c) The lamina terminalis is formed from the rostral
end of the diencephalon.
(d) The pars nervosa of the hypophysis is formed
from the floor of the diencephalon.
(e) The hypothalamic nuclei are formed from the
basal plates of the diencephalon.

Answer 4

D is correct.

• The pars nervosa of the hypophysis cerebri is formed from the floor of the diencephalon. A. The optic vesicle grows out of the forebrain vesicle (see Fig. 18-3). B. The thalamus is formed from the alar plates in the lateral walls of the diencephalon (see Fig. 18-10). C. The lamina terminalis is formed from the rostral end of the telencephalon. E. The hypothalamic nuclei are formed from the alar plates of the diencephalon.

Question 5

The following statements concern the development
of the cerebral hemispheres:

(a) The corpus striatum is formed from the proliferation of the matrix cells lining the roof of the
forebrain vesicle.
(b) The interventricular foramen is formed by the
cavity of the diencephalon.
(c) The choroid plexus of the lateral ventricle
is formed by vascular ectoderm covered by
ependymal cells.
(d) The internal capsule is formed by the developing ascending and descending tracts growing between the developing thalamus and caudate nucleus medially and the lentiform nucleus laterally.
(e) The cortical neurons develop in situ and do not migrate out laterally from the matrix cells lining the cavity of the cerebral hemisphere.

Answer 5

D is correct.

• The internal capsule is formed by the developing ascending and descending tracts growing between the developing thalamus and caudate nucleus medially and the lentiform nucleus laterally (see Fig. 18-11). A. The corpus striatum is formed from the proliferation of the matrix cells lining the floor of the forebrain vesicle. B. The interventricular foramen is formed by the cavity of the telencephalon (see Fig. 18-11). C. The choroid plexus of the lateral ventricle is formed by vascular mesenchyme covered by ependymal cells. E. The
  neurons of the cerebral cortex develop from matrix cells lining the cavity of the cerebral hemisphere. These cells produce large numbers of neuroblasts that migrate out into the marginal zone.

Question 6

The following statements concern the development of myelination in the brain:

(a) Myelination begins at birth.
(b) The sensory fibers are myelinated last.
(c) The process of myelination is haphazard.
(d) Myelinalion of the nerve tracts is largely complete by the fourth year of life.
(e) Myelination is carried out by oligodendrocytes
and not by neurons.

Answer 6

E is correct.

• In the developing brain, myelination is carried out by oligodendrocytes and not by neurons. A. In the developing brain, myelination begins at about the sixth month of fetal life. B. In the developing brain, the sensory fibers are myelinated first. C. Myelination of the nerve tracts is not haphazard but systematic, occurring in different nerve fibers at specific times. D. Myelination of the nerve tracts is largely complete by the end of the second year.

Question 7

The following statements concern the condition of
spina bifida:

(a) It is one of the more common congenital anomalies of the central nervous system.
(b) The most common form of spina bifida is syringomyelocele.
(c) The condition occurs most often in the cervical and upper thoracic regions.
(d) In a myelocele, the neural tube closes in the region of the defect.
(e) Most cases of spina bifida occulta require explorative surgery.

Answer 7

A is correct.

• Spina bifida is one of the more common congenital anomalies of the central nervous system. B. The most common form of spina bifida is spina bifida occulta (see Fig. 18-13). C. Spina bifida occurs most often in the lower thoracic, lumbar, and sacral regions. D. In a myelocele, the neural tube fails to close in the region of the defect (see Fig. 18-13). E. Most cases of spina bifida occulta require no treatment.

Question 8

A 6-month-old girl was seen by the plastic surgeon because of the presence of a swelling at the root of the nose. The mother said that she had noticed the swelling when the child was born and that since then, it had gradually increased in size.

The surgeon examined the child and found the following likely signs except:

(a) The swelling was situated at the root of the
nose jn the midline.
(b) The swelling was located between the frontal
and nasal bones.
(c) The swelling was fluctuant and, on gentle pressure, could be reduced in size.
(d) The swelling was pulsatile, and the pulse coincided with the heart rate.
(e) The pulse did not coincide with the pulse felt
over the anterior fontanelle of the skull.

Answer 8

E is the exception.

• In a cephalic meningocele, the cerebrospinal fluid (CSF) within the swelling is in direct communication with that in the subarachnoid space. The pulsation of the swelling is produced by the pulse wave of the cerebral arteries through the CSF. This pulse wave will coincide with the pulse felt over the anterior fontanelle of the skull.

Question 9

A 6-month-old girl was seen by the plastic surgeon because of the presence of a swelling at the root of the nose. The mother said that she had noticed the swelling when the child was born and that since then, it had gradually increased in size.

The neurosurgeon was consulted, and the following possible additional findings were ascertained except:

(a) A lateral radiograph of the skull revealed a
defect in the membranous bones involving the
nasal process of the frontal bone.
(b) The defect in the membranous bones is known
as cranioschisis.
(c) The condition was associated with a cephalic
meningocele.
(d) There was a herniation of the meninges through
the defect in the skull.
(e) Brain tissue is never found within the hernia.

Answer 9

E is the exception.

• Cranioschisis is characterized by a defect in the membranous bones of the skull through which meninges, or meninges and neural tissue may protrude. The defect usually occurs in the midline in the occipital region or between the frontal and nasal bones. The condition is probably the result of anomalous formation and separation of the neural tube from the surface ectoderm of the embryo.

Question 10

The following statements concern the neural tube:

(a) It is lined by stratified squamous cells.
(b) The neuroblasts migrate medially to form the
intermediate zone.
(c) The repeated division of the matrix cells does
not increase the length and diameter of the
tube.
(d) The ventricular zone will form the gray matter
of the spinal cord.
(e) The nerve fibers in the marginal zone become
myelinated and form the white matter of the
spinal cord.

Answer 10

E is correct.

• The nerve fibers in the marginal zone of the developing neural tube become myelinated and form the white matter of the spinal cord. A. The wall of the neural tube is formed of a single layer of pseudostratified columnar epithelial cells (see Fig. 18-1). B. The neuroblasts migrate peripherally to form the intermediate zone (see Fig. 18-1). C. The repeated division of the matrix cells of the neural tube results in an increase in the length and diameter of the tube. D. The intermediate zone of the neural tube will form the gray matter of the spinal cord.